The present invention relates to electrode antennas, and particularly to an electrode antenna with sufficient reliability, flexibility and durability for use as a sensing element in a system for sensing the presence of a person in a defined space.
As discussed, for example, in U.S. Pat. Nos. 5,914,610 and 5,936,412. The ability to determine the position, orientation or presence of a person within a defined space is important in applications ranging from medical treatments to safety and security. For applications where determining the position, orientation or presence of a person within a defined space is important, sensor arrays have been developed to allow automatic monitoring of the defined space. Such sensor arrays and methods for resolving a presence in a defined space are taught in the above-referenced patents.
Although the method for resolving a presence or activity in a defined space using sensor arrays is known, the ability to adapt those sensor arrays to a particular environment is not addressed in the prior art. Specifically, in uses where the sensor array is used to monitor or detect the presence or activity of a person, additional factors come into play which may greatly impact the acceptance of the sensor array by the individual being sensed. For example, an expected use of these sensor arrays and methods as described in U.S. Pat. Nos. 5,914,610 and 5,936,412 is in an automobile seat for regulating the deployment of airbags. While any variety of electrodes may work suitably for detecting the position, orientation or presence of a person within the automobile seat, if the presence of the sensor electrodes is uncomfortable to the person in the seat, or creates an excessive cost in the production of the automobile, it is less likely that such a system will be accepted by the ultimate purchaser and user of the automobile.
In applications such as sensors in an automobile seat, or other applications where the sensor is placed in close proximity to an individual, factors such as the sensor flexibility, comfort and durability are critical for successful use and acceptance of the sensor array in the intended application. The sensor must be flexible because it is being placed in a flexible or resilient medium (such as a seat cushion), it must be comfortable (undetectable) to the user, and it must be durable so that it does not need to be replaced during the life of the object in which it is placed.
In addition, because it is anticipated that the sensor will be used in high volume applications, it is important that its construction be equally capable of high volume and low-cost production.
The present invention provides a flexible conductive electrode antenna which may be manufactured in high volume and at low cost, while still providing the necessary characteristics of flexibility, flame retardancy, corrosion resistance, abrasion resistance, tear resistance, and electrical reliability. The invention comprises a laminated construction having a layer of conductive material laminated between a layer of flame retardant material and a layer of protective material. The layer of conductive material is preferably a metalized polymer substrate having corrosion resistant properties. Preferably, the polymer is metalized on one side with a layer of copper disposed between layers of nickel. The flame retardant material is preferably a glass cloth laminated to the non-metalized side of the polymer substrate. The protective material is preferably a non-woven material laminated to the metalized side of the polymer substrate.
In an alternate embodiment, the layer of conductive material may comprise a conductive woven or conductive non-woven material. Also, the flame retardant layer may comprise an epoxy tape having a fire retardant component.